The present invention generally relates to information signal recording/reproducing apparatus for recording and/or reproducing an information signal on and from a disk-shaped rotary information recording medium accommodated in a cartridge, and particularly to a mechanism used in such an apparatus for actuating a protective shutter provided on the cartridge.
Conventionally, there is a 3.5 inch flexible magnetic disk accommodated in a cartridge. Such a cartridge has a window for allowing the magnetic disk in the cartridge to make contact with a magnetic head of a magnetic recording/reproducing apparatus for recording and/or reproducing an information signal on and from the disk. The window is closed by a protective shutter when the disk is not used in the apparatus. When the disk is inserted into the magnetic recording/reproducing apparatus for operation, the protective shutter is engaged with a pin provided at a tip end of an actuation arm constituting a member of a shutter actuating mechanism. With further insertion of the cartridge into the apparatus, the arm is pushed by the cartridge and swings in a first direction. Responsive to this swinging motion of the arm, the shutter engaged with the pin at the tip end of the arm is displaced and the window in the cartridge is exposed. When ejecting the cartridge from the magnetic recording/reproducing apparatus, the arm is swung in a second direction opposite to said first direction by an action of a spring urging the arm to its initial state responsive to the withdrawal of the cartridge from the apparatus. Responsive to the swinging motion of the arm in the second direction, the protective shutter, urged so as to close the window by an action of another spring in the cartridge, is closed again.
On the other hand, there is proposed an optical disk accommodated in a cartridge having a construction similar to the cartridge accommodating the 3.5 inch flexible magnetic disk. In such a cartridge designed for the optical disk, too, a window is formed on the cartridge so as to allow incidence of an optical beam on the disk for recording and/or reproducing of an information signal on and from the optical disk. Usually, the length of the window of such a cartridge measured in a direction X.sub.1 -X.sub.2 as shown in FIG. 1 is larger than the corresponding length of the window of the cartridge accommodating the magnetic disk. Therefore, the extent or stroke of movement of the protective shutter is larger in the cartridge accommodating the optical disk as compared to the cartridge accommodating the magnetic disk. Accordingly, one needs a shutter actuating mechanism having an actuation arm with an extended arm length for actuating the protective shutter of the cartridge designed for accommodating the optical disk.
When the length of the actuation arm of the conventional shutter actuating mechanism is increased so as to adapt the mechanism to the cartridge accommodating the optical disk, there is a tendency that the arm, held rotatably on a holder which is a member of the optical recording and/or reproducing apparatus provided movably in the apparatus and into which the optical disk is inserted together with the cartridge, tends to be tilted relative to the holder due to the increased weight, and the parallelism between the actuation arm and the holder is lost. When the parallelism is lost, the pin at the tip end of the actuation arm does not engage properly with the shutter when the cartridge is inserted into the holder. More specifically, the pin at the tip end of the arm misses the engagement with a corresponding depression formed on the shutter. Thus, there is a substantial risk that the shutter is not smoothly opened or closed. As the thickness of the cartridge accommodating the optical disk, and therefore the size of the depression, is substantially reduced as compared to the thickness of the cartridge accommodating the magnetic disk, the problem of the pin at the tip end of the actuation arm missing the proper engagement with the corresponding depression in the protective shutter is particularly serious.